1. Field of the Invention
The present invention generally relates to an antenna structure, and more particularly, to a three-dimensional antenna structure built in an electronic device.
2. Description of Related Art
In keeping pace with progress in telecommunication technology, application of the telecommunication technology for hi-tech products has been increasing and related telecommunication products have become diversified. In recent years, the consumer functional requirements for telecommunication products have become increasingly higher; therefore, telecommunication products with various designs and functions are continuously brought to market, the computer network products with wireless networks are in demand. Since the antenna design affects telecommunication quality of telecommunication products, it is the key factor of telecommunication products.
Generally speaking, antennas have a higher height for achieving the purpose of omni-direction transmissions, such that external antennas are adopted. External antennas comprise monopole antennas, helix antennas and printed dipole antennas. However, in order to reduce the height of an antenna or hide the antenna, the internal antenna usually is a planarized design. Internal antennas comprise microstrip antennas and planar inverted F antennas (PIFA).
FIG. 1A is a three-dimensional diagram showing a conventional microstrip antenna. Referring to FIG. 1A, the microstrip antenna 100 comprises a radiating patch 110, a feed coaxial cable 120 and a ground plane 130. One end of the inner core conductor of the feed coaxial cable 120 is connected to a feed point 112 of the radiating patch 110, such that the radiating patch 110 is connected to a signal source through the feed coaxial cable 120. Further, one end of the outer shielding conductor of the feed coaxial cable 120 is connected to the ground plane 130.
FIG. 1B is a radiation pattern of the microstrip shown in FIG. 1A. Referring to FIGS. 1A and 1B, during signal transmissions, a better signal transmission area is restricted to some specific area since the microstrip 100 has a broadside radiation pattern. More specifically, a better signal transmission area is right above the microstrip antenna 100, and a poor signal transmission area is around the microstrip antenna 100.